Daikin RX18BXVJU
Matched with the FTX18BXVJU indoor unit, this system is certified by ENERGY STAR but not to the cold-climate criteria and publishes 9.00 HSPF2 and 20.00 SEER2, with 11,600 BTU/h of heating at 5°F.
Heating capacity of the Daikin RX18BXVJU at three outdoor temperatures, in BTU per hour. Paired with FTX18BXVJU: 11,600 at 5°F, 14,500 at 17°F, 21,600 at 47°F.
- HSPF29.00Btu/Wh, seasonal heating
- SEER220.00Btu/Wh, seasonal cooling
- COP at 5°F1.80at that test point
- Capacity at 5°F11,600BTU/h
- Share of 47°F capacity53.7%ours: 5°F ÷ 47°F
What these numbers are and are not. SEER2, EER2, HSPF2 and the COP at 5°F are results from a standard rating procedure, measured at fixed temperatures and airflow in a laboratory. They are not predictions for your house, your climate or your winter. Two systems with the same HSPF2 can use different amounts of electricity in the same building, and the same system will perform differently in Boston and in Atlanta. Use the published capacity at 5°F to judge whether a system still produces heat on a cold night; use HSPF2 only to compare systems with each other.
Daikin RX18BXVJU published specifications
| Outdoor unit | RX18BXVJU |
|---|---|
| Indoor unit | FTX18BXVJU (Daikin OTERRA) |
| Cold-climate certified | No |
| ENERGY STAR Most Efficient | No |
| SEER2 | 20.00 Btu/Wh |
| EER2 | 12.50 Btu/Wh |
| HSPF2 | 9.00 Btu/Wh |
| Cooling capacity | 18,000 BTU/h |
| Heating capacity at 47°F | 21,600 BTU/h |
| Heating capacity at 17°F | 14,500 BTU/h |
| Heating capacity at 5°F | 11,600 BTU/h |
| COP at 5°F | 1.80 |
| Compressor staging | Continuously variable |
| Refrigerant | R-410A |
| Date certified | 2026-08-11 |
| ENERGY STAR ID / AHRI reference | 2667590 / 211697900 |
| 5°F capacity as a share of 47°F (ours) | 53.7% |
| Capacity class (ours) | 18,000 BTU/h nominal |
Source. ENERGY STAR Certified Heat Pumps, U.S. EPA, retrieved 2026-10-16 from the dataset's Socrata API. Record identified by ENERGY STAR ID 2667590, AHRI reference 211697900. Certification partner: Daikin Comfort Technologies Manufacturing, L.P.. Model numbers are reproduced exactly as published, including the asterisks ENERGY STAR carries as the manufacturer's wildcard for trim variants.
What the published capacities say about cold weather
A heat pump moves heat from outdoor air, so the colder that air gets, the less heat there is to move. The dataset publishes capacity at three outdoor temperatures, and the shape between them is the single most useful thing on this page. For the RX18BXVJU paired with the FTX18BXVJU:
- At 47°F it delivers 21,600 BTU/h.
- At 17°F it delivers 14,500 BTU/h.
- At 5°F it delivers 11,600 BTU/h, which is 53.7% of the 47°F figure.
ENERGY STAR does not list this system under its cold-climate criteria. It is still a certified heat pump; it simply was not certified against the program's additional low-temperature requirements. In a cold climate that makes the published 5°F capacity above, and any backup heat you plan for, the numbers to look at.
Running cost for a 18,000 BTU/h system like this one
Worked as an illustration, not a quote: a house that burned 600 therms of gas in a year through an 80% AFUE furnace needed about 48.0 million BTU of delivered heat. At $1.50 a therm that gas cost $900. Delivering the same heat with a heat pump rated at 9.00 HSPF2 takes 5,333 kWh, which at $0.18 a kWh costs $960. The two costs are equal at $0.169 a kWh.
Those four prices are not your prices, and HSPF2 is a rating-condition figure rather than a seasonal measurement for your climate. Change every input in the running-cost calculator, which shows each formula as it works.
Comparable systems
Same nominal capacity class (18,000 BTU/h), closest published HSPF2 to this one. Colour marks cold-climate certification.
-
LG KUSAE181A
Standard
HSPF2 8.90 · SEER2 18.00 · 13,300 BTU/h at 5°F
-
LG KUSAH181A
Cold-climate
HSPF2 9.40 · SEER2 21.00 · 13,300 BTU/h at 5°F
-
Daikin RXTH18AVJU*
Cold-climate
HSPF2 9.40 · SEER2 21.00 · 21,600 BTU/h at 5°F
-
Daikin RXF18AXVJU
Standard
HSPF2 9.60 · SEER2 21.00 · 10,700 BTU/h at 5°F
-
Daikin RXF18BVJU*
Cold-climate
HSPF2 9.60 · SEER2 21.00 · 15,200 BTU/h at 5°F
More: all 92 certified systems, or the explainer on SEER2 vs HSPF2.